fix hg log -r ''

mercurial/cmdutil.py

@@ -45,7 +45,7 b' def revrange(repo, revs):'
     """Yield revision as strings from a list of revision specifications."""
 
     def revfix(repo, val, defval):
-        if not val and val != 0:
+        if not val and val != 0 and defval is not None:
             return defval
         return repo.changelog.rev(repo.lookup(val))
 

tests/test-log

@@ -76,3 +76,8 b' hg log --follow-first'
 
 echo % log -P 2
 hg log -P 2
+
+echo '% log -r ""'
+hg log -r ''
+
+exit 0

tests/test-log.out

@@ -185,3 +185,5 b' user: test'
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1
 
+% log -r ""
+abort: Ambiguous identifier!